Azimuthal asymmetries and Collins analyzing power

TL;DR

This paper analyzes azimuthal asymmetries in pion electro-production, successfully reproduces experimental data, and provides new predictions and insights into fragmentation functions and parton distributions.

Contribution

It offers the first extraction of the z-dependence of the Collins fragmentation function and provides predictions for deuteron targets, advancing understanding of spin asymmetries.

Findings

Theoretical reproduction of HERMES data without adjustable parameters.

Extraction of the z-dependence of the Collins fragmentation function.

First information on the e(x) distribution from CLAS asymmetry.

Abstract

Spin azimuthal asymmetries in pion electro-production in deep inelastic scattering off longitudinally polarized protons, measured by HERMES, are well reproduced theoretically with no adjustable parameters. Predictions for azimuthal asymmetries for a longitudinally polarized deuteron target are given. The z-dependence of the Collins fragmentation function is extracted. The first information on e(x) is extracted from CLAS A_LU asymmetry.